Camera lucida

A camera lucida is an optical device used as a drawing aid by artists and microscopists. By looking through the prism in its standard, a user sees an optical superimposition of the subject positioned in front of the device over the surface below. This allows the artist to duplicate key points of the scene on the drawing surface, thus aiding in the accurate rendering of perspective.

The camera lucida was patented in 1806 by the English chemist William Hyde Wollaston.

The basic optics were described 200 years earlier by the German astronomer Johannes Kepler in his Dioptrice (1611), but there is no evidence he constructed a working camera lucida. There is also evidence to suggest that the Elizabethan spy Arthur Gregory's 1596 "perspective box" operated on at least highly similar principles to the later camera lucida, but the secretive nature of his work and fear of rivals copying his methods led to his invention becoming lost. By the 19th century, Kepler's description had similarly fallen into oblivion, so Wollaston's claim to have invented the device was never challenged. The term "camera lucida" (Latin 'well-lit room' as opposed to camera obscura 'dark room') is Wollaston's.

While on honeymoon in Italy in 1833, the photographic pioneer William Fox Talbot used a camera lucida as a sketching aid. He later wrote that it was a disappointment with his resulting efforts which encouraged him to seek a means to "cause these natural images to imprint themselves durably".

In 2001, artist David Hockney's book Secret Knowledge: Rediscovering the Lost Techniques of the Old Masters was met with controversy. His argument, known as the Hockney-Falco thesis, is that the notable transition in style for greater precision and visual realism that occurred around the decade of the 1420s is attributable to the artists' discovery of the capability of optical projection devices, specifically an arrangement using a concave mirror to project real images. Hockney was inspired after seeing drawings by Ingres, which he came to suspect were made with the aid of a camera lucida.

The camera lucida is still available today through art-supply channels but is not well known or widely used. It has enjoyed a resurgence as of 2017 through a number of Kickstarter campaigns.

The name "camera lucida" (Latin for 'light chamber') is intended to recall the much older drawing aid, the camera obscura (Latin for 'dark chamber'). There is no optical similarity between the devices. The camera lucida is a lightweight, portable device that does not require special lighting conditions. No image is projected by the camera lucida.^{[citation needed]}

In the simplest form of camera lucida, the artist looks down at the drawing surface through a glass pane or half-silvered mirror tilted at 45 degrees. This superimposes a direct view of the drawing surface beneath, and a reflected view of a scene horizontally in front of the artist. This design produces an inverted image which is right-left reversed when turned the right way up. Also, light is lost in the imperfect reflection.^{[citation needed]}